This invention relates to the art of diagnosing engines and, more particularly, to improvements in data acquisition for use in determining whether malfunctions exist in individual cylinders of an engine.
The invention is particularly applicable for use in conjunction with providing data as to the operation of compression ignition engines and is described herein with respect thereto; although it will be understood that the invention is not limited thereto and may be used in other applications, such as for providing data as to the operation of spark ignition engines.
Engine analyzers employing data acquisition means are known in the prior art. Examples of prior art patents on this subject include the U.S. Patents to Hanson, No. 3,994,160, Hanson et al. No. 3,942,365, Hanson et al. No. 3,972,230, and Emerson, No. 3,815,411. In general, these patents disclose systems wherein a data acquisition circuit responds to the operation of an engine and obtains a measure of the time interval of each power period. The data representing the time interval of each power period is forwarded to the acquisition circuitry which determines the average speed of each power period since the average speed is related to the reciprocal of the time interval of each power period. Such information does not reflect the actual variations in speed taking place during each power period, but only the average speed. Consequently, only average speed information is employed by the analyzer in determining the existance of any malfunction conditions, such as low power performance.
The present invention provides improvements over that suggested by such prior art. More particularly, the data acquisition circuit incorporated in the present invention provides a plurality of electrical pulses sufficient in number that a plurality of pulses are provided during each power period. Also, the acquisition circuitry includes means for measuring the time interval between successive pulses and then provides a plurality of time interval samples for each power period.